Magnetic random-access memories (MRAMs) are not new but could change your relationship with your computer. In particular, with these memories, your system would not lose data in case of a power outage, it would be faster and consume less energy. Today these memories are still expensive and not totally reliable. But researchers from Johns Hopkins University have now designed irregularly shaped cobalt or nickel nanorings that can serve as memory cells and which could lead to coin-sized hard drives that could store hundreds of movies.
Here is a short description of this discovery.
These "nanorings" can store a great quantity of information. They also are immune to the problem of "stray" magnetic fields, which are fields that "leak" from other kinds of magnets and can thus interfere with magnets next to them.
Chia-Ling Chien, a professor of physics and astronomy at Johns Hopkins, headed up the research team which also included Frank Q. Zhu, a doctoral candidate.
"It's the asymmetrical design that's the breakthrough, but we are also very excited about the fast, efficient and inexpensive method we came up with for making them," said Frank Q. Zhu.
Below are two scanning electron microscope (SEM) micrographs of symmetric (left) and asymmetric nanorings (right) (Credit: Johns Hopkins University).
The asymmetrical design allows more of the nanorings to end up in a so-called "vortex state," meaning they have no stray field at all. With no stray field to contend with, Zhu's team's nanorings act like quiet neighbors who don't bother each other, and thus can be packed extremely densely. As a result, the amount of information that can be stored in a given area is greatly increased.
The researchers also have a patent pending for these ferromagnetic nanorings.
Magnetic nanorings can maintain stable vortex states and hold the potential for information storage. We have fabricated symmetric nanorings on a macroscopic area with ultrahigh areal density. But symmetric nanorings, when the size is about 100 nm, have only 40% of chances to obtain the vortex states, as found by our group recently. In this application, we also disclose a new process for fabricating asymmetric ferromagnetic nanorings. Unlike symmetric rings, the percentage of vortex states in asymmetric rings can be well controlled from 41% to nearly 100% by changing the field angle (0° to 90°). This is of interest to applications in storage devices.
This research work should be available any day now from the Physical Review Letters. Just check this link in the coming days.
Sources: Johns Hopkins University news release, via EurekAlert!, January 11, 2006; and various web sites
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